• Journal of Welding and Joining
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• 제19권1호
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• pp.49-57
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• 2001

In this study, the residual stress fields of multi-pass welded were analyzed by FEA under various geometrical conditions. In order to estimate the effects of pipe geometries on residual stress distribution, welding processes of each model were performed under the same heat cycles. And then, the influence of cutting off the weld bead on the residual stress redistribution was also estimated. From the results, in the range of t/D=0.05, axial residual stresses on the outer surface of the welded pipe were linearly decreased with pipe diameter increase. On the other hand, hoop residual stresses were not influenced by them. And both axial and hoop residual stresses on the outer surface of the welded pipe were increased with pipe diameter increase. But, when t/D was smaller than 0.05, they were converged in the nearly same value. The maximum residual stresses were generated at around HAZ. It in therefore necessary to consider them in welding design, strength evaluation, and analysis of fracture characteristics.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.90-95
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• 2004

In this study, we proposed new method to mitigate tensile welding residual stress for preventing PWSCC in CRDM nozzle. Residual stress analysis using finite element method is performed to confirm benefit of the new method. In case of applying existing method, tensile axial residual stress decrease by about 28% and tensile hoop residual stress decrease by about 33%. In case of applying the new method, tensile axial residual stress decrease by about 32% and tensile hoop residual stress decrease by about 43%. Therefore, we conclude the new proposed method is more effective to prevent PWSCC than existing method.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.163-169
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• 1999

Residual stresses causing stress corrosion cracking (SCC) of thin-walled steam generator U tubes were investigated. The residual stresses were measured by hole drilling methods, and the applied stresses resulting from the internal pressure and the temperature gradient in the steam generator were estimated theoretically. In U-bent regions, the residual stresses at extrados were induced with compressive stress(-), and its maximum value reached -319MPa in axial direction at $\phi$= $0^{\circ}$ in position. Maximum tensile residual stress of 170MPa was found to be at the flank side at position of $\phi$= $90^{\circ}$, i.e., at apex region. Hoop stress due to the pressure and temperature differences between primary and secondary side were analyzed to be 76 MPa and 45 MPa, respectively.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1862-1870
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• 2020

The purpose of this study is to investigate the effect of welding residual stress on operating stress in designing a nuclear turbine welded rotor. A two-dimensional axisymmetric finite element model is employed to calculate the residual stress before and after post weld heat treatment (PWHT), and then the superposition of residual stress after PWHT and operating stress at normal speed and overspeed were discussed. The investigated results show that operating stress can be affected significantly by welding residual stress, and the distribution trend of superposition stress at the weld area is mainly determined by welding residual stress. The superposition of residual stress and operating stress is linear superposition, and the hoop stress distribution of superposition stress is similar with the distribution of residual stress. With the increasing overspeed, the distribution pattern of the hoop superimposed stress remains almost unchanged, while the stress level increases.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1999년도 특별강연 및 추계학술발표대회 개요집
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• pp.331-334
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• 1999

• 터널과지하공간
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• 제5권4호
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• pp.363-375
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• 1995

Critical literature review in this study revealed that there can be a significant influence of the residual stress on the engineering properties of rock. The review also showed that few number of research works on the quantification of the influence was attributed to the limitation of the two classical measurement techniques, viz, X-ray diffraction and mechanical relaxation method. In this study, a new way of approach was sought based on the assumption that residual stress up to the failure. A series of hoop tests conducted onthe samples from the limb of Carboniferous Limestone in Clevedon, England, revealed that (i) there is no preferential orientations of microcracks and minerals which have been widely believed as the main source of the strength anisotropy of rock; (ii) the anisotropy of the tensile strength of the limestone results from the influence of the residual stress; (iii) since jointing commenced within the fold, residual stored strain energy has been released preferentially in the direction perpendicular to the major joints(o$^{\circ}$ and 90$^{\circ}$); (ⅳ) during the hoop test making it much easier to create tensile fracture in these directons, viz 45$^{\circ}$ and 135$^{\circ}$)was released during the hoop test making it much easier to create tensile fracture in these directions, viz 45$^{\circ}$and 135$^{\circ}$;(v) the direction in which the stored strain energy may be presumed to be the least, required the greatest work to cause failure.

• 한국추진공학회지
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• 제1권1호
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• pp.104-110
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• 1997

고강도 알루미늄 합금 링롤재의 급냉, 링 팽창(expansion) 및 링 압축(compression) 응력제거처리 후 잔류응력을 예측하기 위하여 2차원 축대칭 열해석 및 탄소성 해석을 수행하였다. 급냉 및 응력제거처리 후 2단 과시효 처리(T73)된 링롤재에 대하여 3단계 절단법(Three step sectioning method)을 적용하여 링롤재의 두께에 따른 잔류응력 분포를 측정하였으며, 측정결과를 급냉 및 응력제거처리후 잔류응력 해석결과와 비교분석하였다. 링의 급냉후 원주 및 축방향의 잔류응력 해석값은 T73후 측정값과 비슷한 경향을 보였으며, 링의 내면과 외면에서 압축응력을 나타내었고 중심에서 인장응력을 나타내었다. 잔류응력은 링 팽창(T7351) 및 링 압축(T7352) 적용후 T73에 비해 현저히 감소하였으며, 축방향의 제거 효과가 원주방향보다 우수하게 나타났다. 또한 링 압축에 의한 제거효과가 링 팽창보다 크게 나타났다. 링롤재의 응력제거처리는 제거 효과 및 실용성 측면에서 링 압축 공정이 유리하며, 치수제어 및 장비용량 측면에서 링 팽창 공정이 유리하다는 결론을 얻었다.

• 한국압력기기공학회 논문집
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• 제11권1호
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• pp.45-52
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• 2015

Even though a lot of efforts have been devoted to evaluate welding residual stress characteristics of nuclear components, from the view point of accuracy, there are still some arguments in application of engineering estimation schemes. In this paper, three-dimensional finite element analyses (FEA) were carried out to predict residual stress distributions in butt welds of a typical surge line piping. Mesh optimization was conducted and subsequent analysis results such as the axial and hoop stress components along the weld center line and inner wall. Moreover, alternative evaluation was conducted by using three representative equations and their results were compared to those of FEA. Thereby, key parameters affecting to temperature profiles and residual stress distributions were derived as well as an optimum engineering estimation scheme was recommended.

• Steel and Composite Structures
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• 제17권2호
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• pp.173-184
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• 2014

This study aimed to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites. The analytical solution of residual stress field distribution was obtained by using coaxial cylinder model, and the numerical solution was obtained by using finite element model (FEM). Both of the above models were compared and the thermal residual stress was analyzed in the axial, hoop, radial direction. The results indicated that both the two models were feasible to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites, because the deviations between the theoretical calculation results and the test results were less than 8%. In the titanium matrix composites, along with the increment of the SiC fiber volume fraction, the longitudinal property was improved, while the equivalent residual stress was not significantly changed, keeping the intensity around 600 MPa. There was a pronounced reduction of the radial residual stress in the titanium matrix composites when there was carbon coating on the surface of the SiC fiber, because carbon coating could effectively reduce the coefficient of thermal expansion mismatch between the fiber and the titanium matrix, meanwhile, the consumption of carbon coating could protect SiC fibers effectively, so as to ensure the high-performance of the composites. The support of design and optimization of composites was provided though theoretical calculation and analysis of residual stress.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.25-30
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• 2000

Residual stresses induced in U-bending and tube-to-tubesheet joining processes of PWR's steam generator row-1 tube were measured by X-ray method and Hole-Drilling Method(HDM). The stresses resulting from the Internal pressure and the temperature gradient in the steam generator were also estimated theoretically. In U-bent lesions, the residual stresses at extrados were induced with compressive stress(-), and its maximum value reached -319 MPa in axial direction at ${\psi}=0^{\circ}$ in position. Maximum tensile residual stress of 170MPa was found to be at the flank side at Position of${\psi}=90^{\circ}$, i.e., at apex region. In tube-to-tubesheet fouling methods, the residual stresses induced by the explosive joint method were found to be lower than that by the mechanical roll method. The gradient of residual stress along the expanded tube was highest at the. transition region, and the residual stress in circumferential direction was found to be higher than the residual stress in axial direction. Hoop stress due to an internal pressure between primary and secondary side was analyzed to be 76 MPa and thermal stress was 45 MPa.